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Problem of the Day From the pizza shop, James walks 12 blocks south, 22 blocks east, 18 blocks north, and 30 blocks west. What is the least number of blocks that he must travel if he returns to the pizza shop? Course Scatter Plots 14
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7-9 Scatter Plots
Course 2
Warm UpWarm UpProblem of the DayProblem of the DayLesson PresentationLesson Presentation
Warm UpWhich of the following pairs do you think have a cause-and-effect relationship?
1. height and age2. hand span and address3. grade average and shoe size4. temperature and date
Course 2
7-9 Scatter Plots
yesno
noyes
Problem of the DayFrom the pizza shop, James walks 12 blocks south, 22 blocks east, 18 blocks north, and 30 blocks west. What is the least number of blocks that he must travel if he returns to the pizza shop?
Course 2
7-9 Scatter Plots
14
Learn to display and analyze data in scatter plots.
Course 2
7-9 Scatter Plots
Vocabularyscatter plotpositive correlationnegative correlationno correlation
Course 2
7-9 Scatter Plots
To find out if two sets of data may be related, you can make a scatter plot of the data values in each set. A scatter plot has two number lines, called axes—one for each set of data values.
Each point on the scatter plot represents a pair of data values. These points may appear to be scattered or may cluster in the shape of a line or a curve.
Course 2
7-9 Scatter Plots
Use the data to make a scatter plot. Describe the relationship between the data sets.
Additional Example 1: Making a Scatter Plot
Course 2
7-9 Scatter Plots
Type U.S. Only Rest of WorldMammals 63 251Birds 78 175Reptiles 14 64Amphibians 10 8Fishes 70 11Clams 61 2
Number of Endangered Species
Step 1: Determine the scale and interval for each axis. Place the number of animals endangered in the U.S. on the horizontal axis and the number of animals endangered in the rest of the world on the vertical axis.
0 20 40 60 80
300 240 180 120 60 0
Additional Example 1 Continued
Course 2
7-9 Scatter Plots
Type U.S. Only Rest of WorldMammals 63 251Birds 78 175Reptiles 14 64Amphibians 10 8Fishes 70 11Clams 61 2
Number of Endangered Species
Step 2: Plot a point for each pair of values.
0 20 40 60 80
300 240 180 120 60 0
Use the data to make a scatter plot. Describe the relationship between the data sets.
Additional Example 1 Continued
Course 2
7-9 Scatter Plots
Type U.S. Only Rest of WorldMammals 63 251Birds 78 175Reptiles 14 64Amphibians 10 8Fishes 70 11Clams 61 2
Number of Endangered Species
Step 3: Label the axes and give the graph a title.0 20 40 60 80
300 240 180 120 60 0
U.S.
Rest
of W
orld
Number of Endangered Species
Use the data to make a scatter plot. Describe the relationship between the data sets.
Additional Example 1 Continued
Course 2
7-9 Scatter Plots
Type U.S. Only Rest of WorldMammals 63 251Birds 78 175Reptiles 14 64Amphibians 10 8Fishes 70 11Clams 61 2
Number of Endangered Species
There appears to be no relationship between the data sets.
0 20 40 60 80
300 240 180 120 60 0
U.S.
Rest
of W
orld
Number of Endangered Species
Check It Out: Example 1
Course 2
7-9 Scatter Plots
Step 1: Determine the scale and interval for each axis. Place the year on the horizontal axis and the number of farm workers on the vertical axis.
1940 1960 1980 2000
10,000
8,000 6,000 4,000
2,000
1940 8,9951950 6,8581960 4,1321970 2,8811980 2,8181990 2,864
Number of farm workers in thousands
Year
Use the data to make a scatter plot. Describe the relationship between the data sets.
Check It Out: Example 1 Continued
Course 2
7-9 Scatter Plots
Step 2: Plot a point from each pair of values.
1940 8,9951950 6,8581960 4,1321970 2,8811980 2,8181990 2,864
Number of farm workers in thousands
Year
1940 1960 1980 2000
10,000
8,000 6,000 4,000
2,000
Check It Out: Example 1 Continued
Course 2
7-9 Scatter Plots
Step 3: Label the axes and give the graph a title.Year
Num
ber (
in th
ousa
nds)
Number of Farm Workers
1940 8,9951950 6,8581960 4,1321970 2,8811980 2,8181990 2,864
Number of farm workers in thousands
Year
1940 1960 1980 2000
10,000
8,000 6,000 4,000
2,000
Check It Out: Example 1 Continued
Course 2
7-9 Scatter Plots
The number of farm workers decreased from 1940 to 1970.
1940 8,9951950 6,8581960 4,1321970 2,8811980 2,8181990 2,864
Number of farm workers in thousands
Year
Year
Num
ber (
in th
ousa
nds)
Number of Farm Workers
1940 1960 1980 2000
10,000
8,000 6,000 4,000
2,000
There are three ways to describe data displayed in a scatter plot.
Course 2
7-9 Scatter Plots
Positive Correlation
The values in both data sets increase at the same time.
Negative Correlation
The values in one data set increase as the values in the other set decrease.
No Correlation
The values in both data sets show no pattern.
Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain.
Additional Example 2A: Determining Relationships Between Two Sets of Data
Course 2
7-9 Scatter Plots
The graph shows that as area increases, population increases. So the graph shows a positive correlation between the data sets.
Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain.
Additional Example 2B: Determining Relationships Between Two Sets of Data
Course 2
7-9 Scatter Plots
The number of vacation days is not related to height. So there would not be any correlation between these two variables.
height and number of vacation days
Write positive correlation, negative correlation, or no correlation to describe each relationship. Explain. outdoor temperature and coat sales
Additional Example 2C: Determining Relationships Between Two Sets of Data
Course 2
7-9 Scatter Plots
As the outdoor temperature increases, the number of coat sales will decrease. So there would be a negative correlation between the data sets.
Write positive correlation, negative correlation, or no correlation to describe each relationship.
Check It Out: Example 2A
Course 2
7-9 Scatter Plots
Tornado Frequency
0200400600800
10001200
1940 1960 1980 2000Year
Num
ber
of T
orna
dos
The graph shows that as the year increases, number of tornados increases. So the graph shows a positive correlation between the data sets.
Write positive correlation, negative correlation, or no correlation to describe each relationship.
Check It Out: Example 2B
Course 2
7-9 Scatter Plots
Guitar String Frequency
200
300400
500600
700
40 60 80 100 120Length of string (cm)
Freq
uenc
y (v
ps)
The graph shows that as the length of string increases, frequency decreases. So the graph shows a negative correlation between the data sets.
vps = vibrations per second
Write positive correlation, negative correlation, or no correlation to describe each relationship.
Check It Out: Example 2C
Course 2
7-9 Scatter Plots
There would not be any correlation between these two variables.
eye color and age
Lesson Quiz: Part I
1. Use the data to make a scatter plot. Describe the relationship.
Course 2
7-9 Scatter Plots
Temperature Attendance 70 100 80 350 75 250 85 400 74 200 82 375 72 260
Beach Attendance
0
100
200300
400
500
70 75 80 85Temperature
Atte
ndan
ce
The graph shows a positive correlation.
Lesson Quiz: Part II2. Write positive, negative, or no correlation to
describe each relationship. Explain
Course 2
7-9 Scatter Plots
negative correlation; as age increases, attendance decreases.